This disclosure relates to an electrochemical cell, and in particular to an electrode used therein and method of making the electrochemical cell comprising the electrode.
Electrochemical cells are energy conversion devices, usually classified as either electrolysis cells or fuel cells. A proton exchange membrane electrolysis cell may function as a hydrogen generator by electrolytically decomposing water to produce hydrogen and oxygen gas, and may function as a fuel cell by electrochemically reacting hydrogen with oxygen to generate electricity. Referring to FIG. 1, which is a partial section of an anode feed electrolysis cell 100, process water 102 is fed into cell 100 on the side of an oxygen electrode (anode) 116 to form oxygen gas 104, electrons, and hydrogen ions (protons) 106. The reaction is facilitated by the positive terminal of a power source 120 electrically connected to anode 116 and the negative terminal of power source 120 connected to a hydrogen electrode (cathode) 114. Oxygen gas 104 and a portion of process water 108 exit cell 100, while protons 106 and water 110 migrate across a proton exchange membrane 118 to cathode 114 where hydrogen gas 112 is formed.
Another example of a water electrolysis cell using the same configuration as is shown in FIG. 1 is a cathode feed cell, wherein process water is fed on the side of the hydrogen electrode. A portion of the water migrates from the cathode across the membrane to the anode where hydrogen ions and oxygen gas are formed due to the reaction facilitated by connection with a power source across the anode and cathode. A portion of the process water exits the cell at the cathode side without passing through the membrane.
An exemplary fuel cell uses the same general configuration as is shown in FIG. 1. Hydrogen, from hydrogen gas, methanol, or other hydrogen source, is introduced to the hydrogen electrode (the anode in fuel cells), while oxygen, or an oxygen-containing gas such as air, is introduced to the oxygen electrode (the cathode in fuel cells). Water may also be introduced with the feed gas. Hydrogen electrochemically reacts at the anode to produce protons and electrons, wherein the electrons flow from the anode through an electrically connected external load, and the protons migrate through the membrane to the cathode. At the cathode, the protons and electrons react with oxygen to form water, which additionally includes any feed water that is dragged through the membrane to the cathode. The electrical potential across the anode and the cathode may be exploited to power an external load.
In other embodiments, one or more electrochemical cells may be used within a system to both electrolyze water to produce hydrogen and oxygen, and to produce electricity by converting hydrogen and oxygen back into water as needed. Such systems may be referred to as regenerative fuel cell systems.
Electrochemical cell systems may include one or more individual cells arranged in a stack, with the working fluids directed through the cells via input and output conduits formed within the stack structure. The cells within the stack are sequentially arranged, each including a cathode, a proton exchange membrane, and an anode (hereinafter “membrane electrode assembly”, or “MEA”). Each cell may further comprise a first flow field in fluid communication with the cathode and a second flow field in fluid communication with the anode. The MEA may be supported on either or both sides by screen packs or bipolar plates disposed within the flow fields, which may be configured to facilitate membrane hydration and/or fluid movement to and from the MEA. In addition, to maintain intimate contact between cell components under a variety of operational conditions and over long time periods, uniform compression is applied to the cell components, particularly the active area, by pressure pads or other compression means.
However, while existing electrochemical cells, and in particular electrodes used therein and method of making the electrodes are suitable for their intended purposes, there still remains a need for improvements, particularly regarding the amount of catalyst consumed and utilized in making the electrode. Therefore, a need exists for a method of making an electrode comprising less catalyst material consumed with improved activity compared to existing electrodes.